There are only a relatively few ectoparasiticides which are commercially available today. The most popular pediculicidal toxicants are Lindane (gamma benzene hexachloride), Malathion [(S-1,2-dicarbethoxyethyl)-O,O-dimethyl phosphorodithioate], synergized pyrethrins and Cuprex (a combination of tetrahydronaphthalene, copper oleate and acetone, the acetone not asserted to be active). Sulphur and Lindane are the best known agents for scabies. Because of increased concern about the overall safety of some of the known ectoparasitic toxicants, the search for new, safe and effective ectoparasiticides has intensified recently.
Many species of insects encase their ova in protective sheaths which are impregnable to most toxicants. The gestation period of the egg is often relatively long in comparison to the life cycle of the adult forms. Thus, an agent effective only against adults must persist for the lifetime of the developing ovum or must be reapplied as successive hatchings occur. The ideal agent for treatment of ectoparasites should be active against the ova as well as the adult and nymphal forms, and should be relatively non-toxic to the host. Few agents are, however, so active.
The toxicants can be used in the form of shampoos or body washes. In contrast to agents used by inunction, compositions designed to be used as shampoos or body washes must fulfill certain criteria. For example, they must either exert their parasiticidal and/or ovicidal effects within a very short time or must resist washing off during the course of ablutions.
It has now been discovered that a small group of imidazolines and imidazolium derivatives are quite effective as toxicants for insects, particularly ectoparasites or their ova, and aphids. While it has been reported that some other imidazoline derivatives have some activity as insecticides (see U.S. Pat. Nos. 3,996,392 and 3,948,934) and the instant imidazolines are known to exhibit a mild germicidal, germistatic, fungicidal and fungistatic activity, the present imidazolines and imidazolium derivatives exhibit a surprising degree of toxicity against insects, particularly the ectoparasites and their ova, and aphids and such activity can, in some instances, be enhanced by the cojoint use of a lower alkanol.
Accordingly, it is the object of this invention to provide new, safe and effective toxicants for use against insects and their ova, particularly ectoparasites and their ova, and aphids. This and other objects of the invention will become apparent to those skilled in the art from the following detailed description.